The present invention provides insect attractant formulations that can be effectively employed to control insect populations using male annihilation technique (MAT), and insect control methods using the formulations. More particularly, the invention concerns a sprayable or solid biodegradable formulation that includes the insect para-pheromones methyl eugenol and cue lure combined with a biodegradable wax carrier. The formulation is effective to provide for continuous release of methyl eugenol and cue lure from the carrier over an extended period of time to effectively attract members of target insect populations. The formulation can be used without an insect toxicant for mating disruption of insect pests. Alternatively, by including at least one insect toxicant in the formulation, the formulation can be used in an “attract and kill” system for controlling insect populations.
Fruit flies (family Tephritidae) are among the most destructive agricultural pests in the world, destroying citrus crops and other fruit and vegetable crops at an alarming rate and forcing food and agriculture agencies to spend millions of dollars on control and management measures. The term “fruit flies” is used herein to indicate all flies belonging to the family Tephritidae (Diptera), examples of which include Bactrocera dorsalis (Oriental fruit fly), Bactrocera cucurbitae (Melon fly), Dacus tryoni (Queensland fruit fly), Ceratitis capitata (Mediterranean fruit fly), and fruit flies of the genera Rhagoletis and Anastrepha, for example.
Fruit flies cause devastating direct losses to many fresh fruits and vegetables. With expanding international trade, fruit flies as major quarantine pests of fruits and vegetables have taken on added importance, triggering the implementation of area-wide national or regional control programs. Damage to fruits and vegetables is caused by fruit fly larvae which tunnel through fruits and in some cases through stem tissue. Bacteria, which are deliberately introduced into the plant host tissue by the adult female fruit fly along with her eggs, multiply at the expense of plant tissue. The larvae then feed on the resultant bacterial “soup” inside the host tissue which is soon rendered unfit for human consumption.
Substantial attention has been given in recent decades to biological control of fruit flies and other insect pests as an alternative to the use of chemical pesticides. Spraying and similar methods of applying crops with chemical pesticides have historically been the most commonly practiced methods of controlling insect pests; however, there are problems with such methods. For example, spraying insecticides typically does not allow targeting of specific types or species of insect pests, which results in destruction of other types or species of insects that may be beneficial to the crop or to the ecological balance of the area being treated. Also, indiscriminant application methods are wasteful of insecticide, and frequent application is generally required, particularly against mobile insect pests. Another disadvantage of widespread aerial spraying of a pesticidal composition is that it generally affects both the agricultural areas and areas inhabited by people, thus also treating non-target species of mammals and arthropods as well as generating adverse environmental effects.
One method of biological control which has proven successful is the use of synthetic insect sex pheromones for pest control by mating disruption. Since much of an insect's behavior is chemically controlled, there is an opportunity to interfere with the natural chemical communication between insects as a means of controlling insect pests. Pheromones are semio-chemicals, i.e., behavior-modifying chemicals, that act as signals to other insects of the same species. Sex and aggregation pheromones are used by a number of different species to locate possible mates. These can be either single components or mixtures of two or more different chemicals that act in concert. Many pheromones have been identified to date, and many of these compounds can be synthetically produced. Synthetically produced compounds that have pheromone-like effect are referred to herein as “para-pheromones.” Pheromones and para-pheromones are referred to collectively herein as “attractants.” Typically, for mating disruption, a small amount of an attractant is released from a dispenser or carrier material at a level above the concentration released by female insects. When the background level of synthetic pheromone released is above a threshold, male insects are unable to locate female insects. The male's inability to find a mate will then control future populations of the insect pest.
Another method for addressing the disadvantages associated with indiscriminate application of pesticides, which combines features of biological control and pesticide control approaches, involves the use of baits that are adapted to attract particular types and/or species of insects for targeted delivery of insect toxicants. This method enables the selective control of insect pests. An object of this approach is to utilize attractants that selectively draw targeted pests to a lure or trap, while other harmless or beneficial insects in the vicinity are generally not affected. Attractants can be employed in combination with insect toxicants in “attract and kill” systems which utilize the attractants to lure individual insects, typically male insects, of a particular type and/or species to a bait, where the insects then come into contact with an insect toxicant to kill the attracted insects. These types of systems have optimal effectiveness during mating seasons of the insects and optimal effectiveness of such systems relies upon a relatively continuous release of the attractant(s) over an extended period of time, i.e., through typical insect mating periods.
The addition of a pesticide to fruit fly specific attractants is the basis for control by the Male Annihilation Technique (MAT). MAT relies on male fruit flies being strongly attracted to pheromones or pheromone-like chemicals. These pheromones, or analogues thereof, can be used in combination with an insecticide treated matrix to eliminate the males in an area. MAT-based control systems have traditionally used fiber blocks or cotton wads impregnated with cue lure or methyl eugenol (depending on the target species) plus a toxicant to kill the male flies when they are attracted and contact the bait. These ‘attract-and-kill’ devices generally incorporate high concentrations of the toxicant and cause rapid death of male flies that contact them. The formulated attractant/insecticide can be placed in a large number of traps distributed throughout an area in which control or eradication is desired. MAT works by reducing the male population to an extent that mating is effectively eliminated, or at least substantially reduced. MAT is a proven technique to control fruit flies.
More recently, a variation of the MAT approach has been developed that utilizes a biologically inert matrix for the release of semio-chemicals and/or pesticides. This approach is referred to as “SPLAT” (Specialized Pheromone & Lure Application Technology), and involves the use of a waxy biodegradable carrier that is effective to adhere to plant bark or foliage or other structure present in an area to be treated, then slowly erodes from the surface and biodegrades in the soil during or after the period of time during which the semio-chemicals are released and/or pesticides are dispensed.
The para-pheromones methyl eugenol and cue lure (also referred to as “cuelure”) are extremely effective for attracting certain species of insects, but exhibit essentially no attractive effect for other species. For example, fruit flies are very specific in their response to methyl eugenol and cue lure, with prior studies having shown that flies of species that are attracted to methyl eugenol do not respond to cue lure and vice versa. Because the simultaneous attraction of both groups of species would be desirable, attempts have been made to use a mixture of methyl eugenol and cue lure in a single lure or a single fruit fly trap with the objective of providing a system having a broader spectrum of attraction (i.e., attracting fruit flies of more species than are attracted to either methyl eugenol or cue lure individually). Efforts to develop systems utilizing methyl eugenol and cue lure together have not proven successful, however, because cue lure has been consistently shown in multiple reported studies to have an antagonistic or inhibitory effect on the ability of methyl eugenol to attract Oriental fruit flies. Therefore, notwithstanding the benefits such a combination would provide, and notwithstanding efforts to use these two attractants together, cue lure's inhibiting or antagonizing effect on methyl eugenol has prevented the development of combined methyl eugenol and cue lure lures.